Hydrogen makers

By putting bacteria to work, a new bioreactor produces hydrogen hundreds of times as fast as previous prototypes.

In a microbial fuel cell, bacteria break down organic matter, releasing electrons and protons into a solution. The protons migrate through a membrane, while the electrons enter a cathode and pass through a circuit that delivers them to the protons on the other side. There, protons—ionized hydrogen—and electrons react with oxygen to produce water, at the same time generating a voltage that keeps the electrons flowing, so the device produces a small amount of electric power (SN: 2/4/06, p. 72).

In the absence of oxygen, and with the help of a metal catalyst, the protons and electrons will instead combine into hydrogen gas. However, such hydrogen-producing bioreactors require an external voltage to pull the electrons from one side to the other, and so far have been very

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